PEG should give great MALDI mass spectra. Just ask any of us who have protein
samples that contain small amounts of PEG!! Maybe you should try adding some
protein to your sample! Just kidding.
I have two suggestions.
1. Try diluting your sample. 1: 10, 1:100, and 1:100 with matrix saturated
33% ACN/water.
2. Try adding a trace amount of sodium chloride to your sample.
Good luck and let us know what works.
Mike Knierman
knierman@lilly.com
ABRFers,
I am trying to quantitate the molecular weight distribution of PEG and PEG
derivatives (ie proprionic-acid peg) by MALDI tof analysis. I have read a
paper by Williams et al. in Macromolecules (1996), 29:8144-8150 that
describes liquid-phase matrix methods to make this work, but they also
report nice spectra using 5ul alpha-CHCA in CH3CN as substrate and sat'd
sol'n of the same matrix in MeOH:H20:PEG in equal volume of 1mg/ml PEG. I
tried the a-CHCA approach, but cant seem to get it the PEG to fly under
these conditions, and I have toyed around a bit with ratios of analyte to
matrix but still no luck. I have had some helpful suggestions from the
Genetics Institute that doping the matrix with CsCl or AgCl may work (it
works for PS). Does anyone have a protocol for this method, or know of
another sure-fire way to make my peg or peg-cooh fly?
Cheers,
--Gary
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Gary Van Domselaar gvd@redpoll.pharmacy.ualberta.ca
Faculty of Pharmacy Phone: (780) 492-4493
University of Alberta FAX: (780) 492-5305
Edmonton, Alberta, Canada